As Harry said bigger wheels steel rims tend to run lighter than alloys if you don't go too wide you should be ok keep to the width of the mazda tyres, but as Harry also said fitting bigger wheels will take more stopping if you have got the mazda master cylinder and servo I would think you will be ok you will have to get a bit imaginative with the plumbing but it can be done you may not need the servo but it's not a bad idea

Sorry I can't tell you what rims will fit the mazda hubs run a hub round a few breakers and try some van rims but they must fit perfectly with all the studs centered in the mounting holes, even the slightest bit out will lead to snapped studs and lost wheels

Cheers Dai

EDIT Remember you can always go down a size or two on the tyres to take a bit of stress of the brakes studs etc, also car tyres are a lot lighter than van one's, budget brand tend to be lighter than premium just don't go for low profile
You may find that tyres with a high profile on the rims you have will up the gearing enough presuming you have the low profile tyres from the mazda still fitted

EDIT another thing if you change from alloys to steel rims you will need open top wheel nuts, the studs will be fine, you could cut the dome off the nuts you have but your better off getting new

A mate of mine was running a GS 850 G engine with a escort diff it was low geared but he didn't get left behind that had 14" rims with high profile tyres fitted

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Dyslexic Dai

Last edited by wiskers; 28-04-2016 at 07:54 AM.
Reason: Bit after the word edit